1. Field of the Invention
This invention relates to method and apparatus for the manufacture of glass panel screens for monitors and television picture tubes, and more particularly to a glass panel screen machine that permits a plurality of adjustments to be efficiently made to the machinery for coating the glass panels of television monitors and the like.
2. Description of the Prior Art
The screen of a cathode ray tube for television monitors is coated with a plurality of colored dots or pixels. These dots glow under the impact of high-speed electrons. Conventionally the pixels are red, green, and blue on a black background.
A process for applying the colored pixels to the glass screen of a cathode-ray tube is disclosed in U.S. Pat. No. 3,319,759 and involves a sequence of steps performed at a number of stations arranged in a circuit. An individual glass panel or screen is automatically advanced from station to station where individual operations are performed in applying colored pixels to the screen in a preselected fashion. With this device each screen is supported by a workholder mounted on a cart which moves along a conveyor from station to station. The relative position of a screen at each station is controlled by motors for effecting rotational and tilting motion of the workholder. The movement of the screens from work station to work station is controlled by a drive system that includes a driving motor and a driving clutch element engageable with a driven clutch element. Separate drive systems generate rotational and tilting movement of the workholders at the stations.
U.S. Pat. No. 3,832,211 also discloses a process for the manufacture of cathode ray tube front panels in which a plurality of work stations are equally spaced around the perimeter of a conveyor. A processing operation occurs at each work station. Workpiece holders on the conveyor carry a picture tube panel from one work station to another in a step-by-step fashion. Each panel is supported with the front side up so that its phosphor coated surface is directed downwardly toward washing devices, lacquer application devices and the like. At each work station the rotational speed of a panel is selected based on the processing operation to be performed. The speed selection is accomplished by activation of selected speed control switches that move with the conveyor into contact with cams positioned at each station. By varying the position of the cams at the work stations, one or more switches are activated to cause the motor to run at a predetermined speed.
U.S. Pat. No. 3,364,054 discloses in a process for making phosphor screens for cathrode ray tubes a method for salvaging an excess of phosphor slurry applied to a faceplate panel. During the various operations the faceplate panel is supported by a carrier movable along fixed rails. A drive system generates rotation of the panel at preselected rates and angles of rotation at each work station depending on the operation to be performed.
A number of other approaches have been taken to select and control the angular positions for rotation and speed of rotation of glass panels in screening operations. Specific examples are disclosed in U.S. Pat. Nos. 2,770,557; 2,769,733; and 3,376,153. While it is known to apply a plurality of phosphor layers on a glass panel for a cathrode ray tube to form a triad arrangement of colored dots. The known apparatus utilizes a plurality of work stations arranged in a circular conveyor path. The rotational speeds and angles of tilt of the panels at each station must be individually controlled. The present arrangements do not facilitate adjustments to be made in panel tilt angles or rotational speeds without shutting down the process for considerable periods of time, thus delaying production.
Therefore there is need for a screen machine system that permits rapid and efficient adjustments to be made in the various operations that are performed on the screen at the individual stations and in the movement of the screen from station to station.